支持Topic编辑

添加topics/:id/edit支持. rubychinaspa中的使用方式如下:
```javascript
rubychinaControllers.controller("TopicEditCtrl", ['$scope', 'Photo', '$location', '$routeParams', 'Topic',
  function TopicEditCtrl($scope, Photo, $location, $routeParams, Topic){
    $scope.topic = Topic.get({id: $routeParams.id})
    var dealTopic = function(){
      $scope.topic.$save(
        function(successResult) {
          console.log("/topics/" + successResult.id)
          $location.path("/topics/" + successResult.id)
        },
        function(errorResult) {
          if(errorResult.status === 404) {
              alert('some wrong ')
          }
        }
      );
    }
    $scope.createTopic = dealTopic;
  }
]);
```